Coadministration of Lorcaserin and Phentermine for Weight Management: A 12-week, Randomized, Pilot Safety Study

Obesity (Silver Spring). 2017 May;25(5):857-865. doi: 10.1002/oby.21811.


Objective: To assess the short-term tolerability of lorcaserin alone or with two dose regimens of phentermine.

Methods: This was a 12-week, randomized, double-blind, pilot safety study of N = 238 nondiabetic patients with obesity or overweight with ≥1 comorbidity randomized to lorcaserin 10 mg twice daily (BID; LOR BID) alone or with phentermine 15 mg once daily (QD; LOR BID+PHEN QD) or 15 mg twice daily (LOR BID+PHEN BID). Patients reporting ≥ 1 of 9 potentially serotonergic adverse events (AEs), mean weight loss (WL), and ≥5% WL are reported.

Results: N = 238 were randomized, and N = 235 were treated. N = 94 reported potentially serotonergic AEs: 37.2% LOR BID, 42.3% LOR BID+PHEN QD, and 40.5% LOR BID+PHEN BID. AEs leading to discontinuation were reported approximately twice as often in the LOR BID+PHEN BID group versus the LOR BID group. Mean WL was 3.5 kg/3.3%, 7.0 kg/6.7%, and 7.6 kg/7.2% for LOR BID, LOR BID+PHEN QD, and LOR BID+PHEN BID, respectively. At least 5% WL was achieved by 28.2% LOR BID, 59.0% LOR BID+PHEN QD (P = 0.0002 vs. LOR BID), and 70.9% LOR BID+PHEN BID (P < 0.0001 vs. LOR BID) patients.

Conclusions: Phentermine added to lorcaserin enhanced short-term weight loss but did not increase incidence of potentially serotonergic AEs; however, phentermine twice daily increased discontinuation compared to both lorcaserin alone and lorcaserin plus phentermine once daily.

Trial registration: NCT01987427.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Adolescent
  • Adult
  • Anti-Obesity Agents / administration & dosage
  • Anti-Obesity Agents / pharmacology
  • Anti-Obesity Agents / therapeutic use*
  • Benzazepines / administration & dosage
  • Benzazepines / pharmacology
  • Benzazepines / therapeutic use*
  • Double-Blind Method
  • Female
  • Humans
  • Male
  • Middle Aged
  • Phentermine / administration & dosage
  • Phentermine / pharmacology
  • Phentermine / therapeutic use*
  • Pilot Projects
  • Weight Loss / drug effects*
  • Young Adult


  • Anti-Obesity Agents
  • Benzazepines
  • lorcaserin
  • Phentermine

Associated data